Lust
by Oliviet
Summary: She wanted him. She wasn't supposed to want him. He was her partner. Castle was her partner. Based off of the SVU fic "Ropes" by MaddyM.
1. Chapter 1

AN: So I have this set sometime after Knockdown and before Knockout and I realize that wasn't exactly summer and summer is what they spend apart after she gets shot, but humor me for the purpose of this fic and pretend like summer came sooner. Also I definitely got this story idea from an old SVU fic called "Ropes." Props go to MaddyM, wherever she is these days, for inspiring me.

* * *

Months. It had been months. And yet she still couldn't stop thinking about him and that kiss. She had become increasingly flirty with him over the weeks that had followed without even realizing it. She didn't know why she was doing it. Why she was suddenly going down this road she had almost taken last summer when he had invited her to go to the Hamptons with him. Especially when she was already in a steady relationship.

But the way he had kissed her had left her wanting more. Wanting things she shouldn't be wanting from him. This was Castle, for Christ's sake. She shouldn't be wanting anything from him. She shouldn't still be hung up on that goddamn kiss _months_ after it had happened. But here she is, attempting to read a case file, as her mind wonders back to the thought of his lips and tongue.

She needs to stop.

"Can I get everyone's attention for a moment?" Montgomery asks, walking out of his office and into the squad room. "I just got word from the Commissioner that the entire NYPD will be undergoing some team building exercises over the course of the next few weeks."

A collective groan echoes around the room.

"I know, I know, but it involves some paid vacation time," he tells them, trying his best to sound hopeful. "Next weekend, our squad will be heading upstate to participate in a ropes course that is supposed to help strengthen our unity as a team and between partners."

"Our whole squad?" Ryan asks in disbelief. "What about our cases?"

"Another precinct will be handling our cases for the weekend and we will be returning the favor when they get sent out to the course."

"Seems like more trouble than it's worth," Beckett mumbles, continuing to stare down at the file she had been reading.

"I know it's a hassle," Montgomery starts. "But the head honchos believe this could be some good press and so it's happening. I'll e-mail out the course details to everyone later today."

The squad turns their attention back to their tasks at hand, still muttering about the team building. Montgomery makes his way over to Beckett.

"Beckett?"

She looks up from the file.

"I've received special permission for Castle to attend the course with us."

Her eyes widen. "Wait, what? Why?"

Oh no. Do not stick her with him for a weekend of bonding activities. That's not going to end well. Disaster. That's how that's going to end.

"This course requires a partner and he's yours."

_He's yours_. Her partner. Castle was her partner. That had become increasingly clear in the past couple of months. He didn't just follow her around like a lost puppy anymore. He actually helped, actually managed to save her life a couple of times. But did that make him an integral part of the team that needed to participate in team building? _Castle. Her partner._

"Sir –" she starts, hoping that she can get herself out of it.

"I'm not arguing with you on this one, Beckett. Castle's coming. I've already informed him and he's rescheduled a meeting with his editor to come with us."

"Exactly. _His editor_. He's a writer, not a cop."

"It's not police training or anything. He'll be fine," Montgomery says over his shoulder as he heads back to his office.

Beckett sighs, turning back to her file. This is going to be a long weekend.

* * *

"I'd like to welcome you all to Greek Peak Mountain Resort," a tall man with muscular arms greets them when they arrive at the camp. "My name is Jared Meyers and I'm the director of this course. I'm very excited to have this special partnership with the NYPD this summer."

"I can't believe you actually agreed to come to this," Beckett whispers as Jared keeps talking.

"Well as your partner, I'm required to have your back," Castle grins, already enjoying this way too much. "And besides, it sounded like it could be fun."

"I think you and I have different definitions of fun."

"So I'll go ahead and let everyone get settled into their rooms before we begin our first activity," Jared continues. "Room assignments are organized by partners to further enhance the bonding."

"Oh great, I get to listen to you snore all weekend," Esposito groans, shooting Ryan a look.

"Hey, Jenny bought me these new nasal strips and she says they really help," Ryan protests.

Esposito shakes his head.

"Excuse me," Kate starts, trying to get Jared's attention. "Do even co-ed partners have to share rooms?"

The man nods, acting overly excited about it. "All part of the bonding experience."

Castle sidles up next to her, hefting his backpack back over his shoulder. "Don't worry; I'll be a gentleman about it."

Unbelievable. Absolutely unbelievable. She had to share a room with him now. Share a room with the man whose mouth she couldn't stop thinking about it. This was so not going to end well.

Beckett mumbles something incoherent and takes off in the direction of the cabins. Castle trails behind her.

"Hey, it could be worse," he tries to tell her. "We could be sharing a bed. Although –"

"Castle."

He shuts up and follows her the rest of the way to their cabin in silence. Beckett opens the door to reveal two twin beds, two dressers, and a small sink with a mirror over it.

"Where are the bathrooms?" she asks through gritted teeth.

"You really weren't listening were you?" Castle asks, claiming the bed on the right side of the room. "Communal showers and toilets, right behind our cabin a little ways."

She groans, scrubbing a hand through her hair and sinking down onto the bed on the left.

"You really don't want to be here, do you?" he asks, pulling a stack of clothes out of his backpack to put in the dresser.

"No, no. I want to be back in the city looking for the guy who killed Linda Harris, not taking a weekend vacation out here in the middle of nowhere to become besties with my coworkers."

"How long you are going to let work be your whole life?"

Beckett scrunches her eyebrows together. "Being here _is_ for work."

"No, I mean you should let yourself have fun and relax here. I know you, Beckett. You have a lot of unused vacation days saved up. Take advantage of the weekend off and stop stressing over murders. The other precinct will find Linda's killer."

"I have plenty of fun outside of work, thank you very much."

"What, with that boyfriend of yours who's never around?"

Beckett stills her movements over her open backpack. "This is so none of your business."

Castle shrugs, tossing his now empty backpack under his bed. "Just sayin'. You deserve some fun."

"Did you miss it earlier when I told you that this isn't my idea of fun?"

"At least _try_ to lighten up a bit, Beckett," he says, pushing open the cabin door. "Not working this weekend will only be worthwhile if you let it."

* * *

"Our first activity is meant to test how well you all really know each other," Jared explains once everyone has settled in and circled up on the grassy knoll. "You'll go around and share two truths and one lie about yourself and then your colleagues will have to guess which one is the lie."

"Are we 12?" Beckett mutters loud enough that only Castle and the boys hear.

"Where's Montgomery?" Castle asks, ignoring her comment.

"They have him doing some other course with a couple of other captains that got pulled this weekend," Ryan explains. "No partners and all."

"All right, who wants to go first?" Jared points at Esposito. "How about you?"

"Okay well um," he stammers, caught off guard. "What don't you guys already know about me?"

He rattles off some facts that Ryan sees right through and guesses the lie as soon as his partner's done speaking.

"If you think it's so easy, then you try it," Esposito challenges.

Ryan does, easily stumping the whole squad, and sends a victorious, gloating smile in his partner's direction. Castle goes next. Beckett knows his third fact is a lie before he even says it, and almost doesn't let him finish. His truths, much like Esposito's, were too obvious. They get through the rest of the squad before the circle completes with her. She lets out a deep sigh, still not interested in playing the game.

"I'm really good at cooking breakfast foods. I love strawberry milkshakes. And umm I hate soap operas."

"The third one," Castle says, picking at a blade of grass. "You Temptation Lane fan, you."

"Beckett, you actually watch that crap?" Esposito asks, stifling a laugh.

"She used to watch it with her mom," Castle tells him, shutting him up instantly.

Beckett just nods, shooting him a thankful glance.

"Good," Jared claps, taking control of the group again. "Dinner will be served shortly, and then I suggest you consider calling it an early night. The course will begin at 8 am tomorrow morning, and while tomorrow is just low ropes, I don't want any sleep-deprived injuries on my hands."

"Doesn't he know we're used to running on zero sleep?" Ryan mumbles.

"I'm telling you," Beckett starts, standing up and brushing the grass off of her shorts. "He thinks we're 12."

* * *

Beckett stares into the crackling fire, watching the sparkling embers dance around in the firewood. She stretches her legs out in front of her, leaning back against a log and taking a long sip of her beer. She keeps thinking about that stupid game and how quick Castle was to answer her. She'd forgotten that she made him breakfast that morning after her apartment blew up. Which leads her to another thought: she'd forgotten that he more than likely has seen her naked.

Beckett shakes her head, telling herself it means nothing. She knew Castle's lie just as fast. And as for the naked thing…

Castle sits down beside her wordlessly, passing her a marshmallow skewered on a stick.

"This really is fucking summer camp," she says, holding her stick out over the fire.

He holds his own stick out next to hers, placing the ziplock bag of chocolate and graham crackers between them. He holds his beer in place between his knees so he can twist the cap off and takes a drink.

"Are you really afraid of heights?" she asks after a beat of silence, recalling his lie from the game.

"Well I'm not a natural red head, am I?"

"I don't know; the rest of your family is."

Castle throws her a look and she smiles. "I got stuck on the top of the ferris wheel when I was eight. The thing just broke down and I was up there for an hour by myself."

"Where was Martha?"

"Oh I had 'run away' to Coney Island over some stupid argument I don't even remember."

She laughs, pulling her marshmallow away from the fire to test it. Satisfied, she pulls open the ziplock bag to finish making her s'more.

"The high ropes going to be a problem for you on Sunday?"

He takes another sip of his beer, watching his marshmallow catch on fire. "I'll push through."

Castle makes his own s'more, setting his stick to the side with Beckett's. The silence is comfortable as they eat; the crackling fire, crunching crackers, and nighttime forest noises filling the air.

"Look, I'm sorry about that crack I made about Josh earlier," he apologizes after he finishes licking off his fingers.

She shrugs, finishing off her last bite.

"How are things between you two anyway?"

"How are things between you and Gina?"

"Well considering Gina and I broke up, that bad huh?"

She sighs, taking another swig of her beer. "I don't know, Castle. I really don't."

"It's the sex, isn't it? He looks like one of those types. All talk and no action. Either that or really bad action."

Beckett groans, chucking the cap of her beer at him. "I am not discussing my sex life with you."

"Isn't that part of the _bonding experience_?" he asks, wiggling his eyebrows and mocking Jared.

"You know, I kind of don't think it is."

"Come on, Beckett," he persists, poking her. "Tell me."

"Why do you even care?"

He doesn't respond, continuing to stare at her with the moonlight reflecting off of his eyes. He does have lovely eyes. And a very masculine jawline. A jawline which she had been privy to kiss a few months ago. And that kiss…She catches herself staring at him and shakes her head.

"You know what, I'm just going to go shower and head to bed," she says, starting to push herself off of the ground.

"I accidentally overheard you talking with Lanie the other day," Castle calls after her. "And just for the record, I'm very good at what you have to fake with him."

* * *

The whole way to the showers she'd been raking her brain for exactly what conversation it was that Castle had overheard. About halfway there, she remembers complaining to Lanie about how bad Josh was at oral sex. She almost trips over her own feet at the realization.

_I'm very good at what you have to fake with him._

Now why the hell was he telling her that? Why did she care that he was good at making women come with just his mouth? No matter how good it had felt when he slipped that tongue of his in her mouth last month, how did she know that wasn't just his ego shining through?

_I'm very good at what you have to fake with him._

Beckett makes it to the communal bathroom and grips the edges of the small sink, unable to stop her hands from shaking. He wants her too. The realization hits her like a train. He's taken the flirting level up a notch and… fuck. Her eyes slip closed, her mind flooding with images of Castle's mouth on her.

That masculine jaw line pressed against her. His tongue relentlessly taking and taking until her thighs started shaking and her toes curled and her back arched.

Fuck.

She wanted him.

She wasn't supposed to want him. He was her _partner_. And she had a boyfriend. She was probably only turned on by the thought because it had been so long since she had received oral sex. Correction: good oral sex. There's no way she could actually want Castle in that way. Right?

Beckett starts to slip her hand down the front of her shorts, craving friction, needing something, _anything_, to stop the throbbing between her legs. But then the bathroom door swings open and another officer from their squad walks in, causing her to pretend she was simply fixing her shirt. She gives the officer a nod as she exits the bathroom. It isn't until she's outside that she realizes she intended to take a shower.

"Fuck it," she grumbles, heading back to her cabin.

She had planned to wear her hair up tomorrow anyway.


	2. Chapter 2

"Our first low ropes exercise, involves partner teamwork," Jared explains the next morning.

He gestures toward two poles with two ropes attached to them. One of the ropes is about two feet off the ground and the other hangs above it a couple of feet.

"You and your partner will start on opposite ends of the rope and will have to switch places, without stepping off of the bottom rope," he continues to explain. "If at any point during the exercise, you or your partner makes contact with the ground, you'll both have to return to your starting positions and try again. Any questions?"

The squad files into a line behind the start of the course, and two rookie cops volunteer to go first.

"Did you ever do _this_ at summer camp?" Castle asks, coming up beside Beckett.

He hasn't been able to take his eyes off of her all morning and he's not entirely sure why. Sure, it's a rare occasion to see her in shorts and a tank top, out of her work clothes. And sure, she wears her hair up at work a lot, but when she does, it doesn't normally leave all that extra skin exposed. And to top it all off, he can't keep kicking himself for that comment he made to her last night before she left the campfire. Hitting on Beckett? The only place that's going to get him is kicked out of their cabin.

Beckett shakes her head, letting out a yawn. "Nope. But I'm sure if we just watch a few groups, we'll be able to see what works and what doesn't and get through it quickly."

He wants to bring up last night. Apologize for it. Tell her he was out of line. But they share a room and she hasn't said anything about it yet, so maybe she didn't even hear him say it. Or maybe she's just pretending it didn't happen. Sometimes that's just the best solution, right?

"It's awfully hot out for how early it is," she mumbles, pulling her ponytail out and resecuring it as a bun.

Which leaves even more skin exposed. Even more skin that he just wants to bite into until –

"Castle!"

"Huh, what?" he says, shaking the dirty images out of his head.

She tilts her head, indicating that the line has moved and that he's holding everybody up. He shuffles forward to stand by her side again.

"Learn any techniques yet?" he asks.

Her face pales as she stares back at him. "Techniques?"

Castle stares back at her confused. "Yeah, you said you were going to watch other teams go and –"

Her face immediately reddens. "Oh right yeah, of course." She turns her head to watch two of the older squad members try to get across. They get to the point where they need to switch and one of them just hops off the rope. "Don't do that."

He stares at her intently. Her mind had gone somewhere else when he asked about techniques. Maybe she did hear him last night after all. He takes the risk.

"What other techniques would I have been referring to, Beckett?"

"I, uh, I don't know. That's why I was confused."

Oh yeah. She definitely heard him last night.

* * *

It gets to be their turn to head across the rope. Finally, she gets a break from Castle pestering her about techniques. She hates that she hasn't been able to get the thought of his mouth on her out of her head. She hates even more that he knows it now, since she originally misinterpreted "techniques" to be a sexual thing. And he's been nothing but smug about it ever since.

Beckett steps onto her side of the rope, her fingers wrapping around the rope tethered overhead as Castle does the same.

"We need to take turns moving," she calls across to him. "It helps with balance."

"And I assume you want to go first," he calls back.

She's not sure if that was meant to be an insult or not. "Well I was planning on it because –"

"Just go, Beckett. I'll watch and move next."

She huffs and slides forward on the rope, testing her balance as she moves a little bit further. She pauses and waits for Castle to move, before she goes again. They get a rhythm going, like they're actual partners who know each other's movements like the back of their hands instead of simply a writer and his muse.

Montgomery's words echo in her head as she waits for Castle to take the last few steps toward her. _The course requires a partner and he's yours_.

"Now what?" Castle asks, his hand bumping into hers on the top rope.

"One of us should stay still as the other moves around to the other side."

"I'll stay," he offers, tightening his grip on the top rope. "Go ahead. When you're ready."

Beckett releases the grip of one of her hands and regrabs the rope between Castle's hands. She shifts her weight forward, swinging one of her legs between his on the lower rope. And that's when the trouble starts.

She's straddling one of his legs, he's straddling one of hers, and her chest is pressed up against his. She tells herself that she just has to keep moving, to not think about where her body is pressed. But as she starts to shift her weight again, her foot slips and Castle drops one of his hands from the top rope to catch her.

He's pushing her against him, harder than he needs to, and she's having trouble breathing. Her hips are grinding against his thigh and her eyes slam shut at the contact. She's needed friction there since last night, and now she has it. She rolls her hips once without thinking, hears Castle hiss in her ear.

Beckett opens her eyes and looks up at him. He's staring back at her, his eyes dark and hooded. She feels the beginning of his erection pressing into her inner thigh. Oh god.

"Don't move," he says, releasing his hand from her back to grab back onto the top rope.

"How much longer do you suggest we stay like this?"

She tries yet again to shift her weight, and only ends up pressing herself against him harder.

"Kate."

He rarely calls her by her first name. And when he does, it never sounds like _that_, all guttural and dripping with need.

Double fuck.

"Castle, we have to finish."

He groans, no doubt at her poor choice in words, but doesn't respond. Instead he tries to shift his weight backwards, away from her.

"Stop it before you fall."

He complies, bringing his weight forward again. But it backfires and his thigh rubs against her clit in just the right way. She audibly gasps at the contact, nearly falling again herself. Castle catches her yet again, pulling her close to steady her.

"You heard me last night, didn't you?" he says into her ear. "What I said about Josh?"

Beckett looks up at him, already managing to finally slip past him on the rope. "You think you can handle me, Castle?"

He gapes at her as she finally untangles herself from him to stand on his other side.

"I think the better question is, Beckett, do you think you can handle me?"

And with that he turns around and walks to the other end of the rope, leaving her speechless in the middle.

* * *

This was a whole new level to their relationship. He'd gotten used to pulling her pigtails as she had so eloquently phrased it last year. And clearly she had become accustomed to it as well. But this was a particular brand of teasing he had never had the pleasure to partake with her. Not until now.

He'd snuck up behind her in the lunch line, leaving enough distance to deter questions, but standing close enough to drive her crazy. He noted the way her breathing had sped up, caused just by his proximity. Later, he snuck his hand under the back of her shirt while they were getting instructions for a new activity. His fingers danced over her bare skin, leaving goosebumps in their wake, and sending shivers down her spine.

Not once had she yelled at him, told him he was crossing some sort of line. Not once had she tried to tell him that she was with somebody and that they shouldn't. She just let it happen, let her body respond to his every touch. It was driving him mad.

It made him need to know things he shouldn't. Like how her hips would move once he was inside of her. And what sounds she would make as he pulled an orgasm out of her. And if he could make her moan the way he had just by kissing her when they were trying to distract that guard.

He hadn't forgotten what Kate Beckett tasted it. And he'd bet anything that she could still taste him too.

She saunters up to him after their fifteen minute break before the final activity of the day. She's grinning, almost mischievously.

"Okay, I'll bite. What?" Castle asks as Jared begins his instructions.

"Look, I don't know what's going on here, between us, but…I just got off the phone with Josh. It's over."

His eyes widen. "Beckett –"

"I was going to do it anyway, when we got back. But this way I don't have to feel guilty about whatever happens."

"And what's going to happen?"

Her hand slides up the back of his shirt, mocking his motions from earlier. "You tell me."

Castle visibly swallows and completely misses whatever the hell the next exercise is supposed to be. Because Kate Beckett is single. And her hand is up his shirt.

* * *

She was crazy. Certifiably insane. She broke up with her sweet, smart, doctor boyfriend so what, Castle could eat her out in the comfort of their own little cabin? This wasn't happening. What the hell was she doing?

Beckett buries her head in her hands as she sits at the picnic table, waiting for the dinner line to get shorter. Her stomach is already twisted in knots and she's not sure if she could even keep anything down. She just broke up with Josh, _for Castle_. The man whom last week she didn't want coming on this trip for the fear of how much he'd annoy her. The man whom she almost agreed to go away to the Hamptons with last summer, and would have had he not decided to get back together with his ex-wife at the last minute.

When did their relationship get so damn complicated?

She feels him sit down beside her and slide a plate of food in front of her. She lifts her head.

"You know how I like my burgers?" Beckett asks, raising an eyebrow at him.

Castle shrugs. "I've been with you to Remy's enough times. You always order the same thing. It's not that much different from knowing how you like your coffee, really."

She smiles glancing over at his plate. "You picked all of the cantaloupe out of my fruit salad."

He shrugs again. "You won't eat it."

Maybe it was because she and Josh really weren't together for that long, but he wouldn't have known how to make her burger or to pick out the cantaloupe for her. He didn't know her. Not like Castle did.

Maybe she did make the right decision after all.

"Do we really eat together that often that you know all of my preferences?"

"Think about it, and I'm sure you'll know some of mine too."

She does, her lips curling into another smile. "I know your Chinese order by heart. And that you hate broccoli."

He shudders, spearing a cantaloupe slice with his fork. "Who actually wants to eat a mini tree?"

Beckett laughs, pushing the fruit salad around her plate.

"Are you not hungry?" Castle asks.

She stabs a strawberry and lifts it to her lips. "I thought I wasn't, but maybe I am."

"Kate –"

There it is. Her first name again. She drags her gaze up to meet his.

"What exactly are we doing?"

She stabs another strawberry. "Can we not put labels on it? Just see where it goes?"

"Any particular place in mind you want it to go?"

Beckett hums, picking at the bun on her burger. "Show me what it's like not to have to fake it."

He nearly spits out the water he just took a swig of as Ryan and Esposito sit down across from them.

"You okay man?" Esposito asks, as Castle starts coughing.

"Just went down the wrong way," Castle says between coughs. "I'll be fine."

He shoots a sideways glance at Beckett. "More than fine."

* * *

Tonight she determines that she's actually going to make it to the shower. No more getting sidetracked at the sink by the thought of Castle's tongue. Although the probability of her actually experiencing Castle's tongue has just increased greatly. Because they're "seeing where this goes." Whatever the hell "this" is.

They needed to talk about it and she figured they probably would tonight. Kind of hard not to when they're sharing a room. She could tell that he wanted to get into it at dinner, but Ryan and Espo were headed their way and she couldn't very well just tell them they were having a private conversation and they couldn't sit with them. They'd demand details, being the nosey, almost brother-like, friends that they were.

So she'd ended their discussion with sexual innuendo, something which appeared to affect Castle more than it usually does. During their final activity of the day after dinner, she noticed he'd been extra handsy, using any excuse to touch her.

He'd had his hands on her all day, but this activity was different. They were supposed to guide their blindfolded partner across a small wooden plank. When he had gone across, she had offered him her hand for support. He'd taken it, but instead of just holding it like a normal person, he had rubbed circles onto the back of her hand with his thumb the whole time, sending her mind straight to the gutter with images of that thumb being between her legs instead.

When it was her turn, he'd grabbed her hips the second she stepped on top of the plank. As she started walking across, his hands shifted so one of them was pressing into her lower back and the other was holding her hand. She didn't need all of the support he was offering her. Quite frankly, she thought she could make it across without him touching her at all. But she enjoyed the feeling of his hands on her a little too much and that scared the shit out of her.

Beckett walks into the shower section of the communal bathroom, trying to push him out of her head for the time being. She notes the flimsy shower curtains separating the stalls and the dinky little hooks to hang clothes on. She's back in college living in the dorms, only this time the bathrooms are co-ed. She groans, stepping behind one of the curtains in the corner and stripping out of her clothes. She wishes she had known this would be the situation and she would have packed a robe.

She moves to turn on the shower and sees that it's just one of those detachable shower heads. She starts to let out another groan of frustration with this place, when her mind re-enters the gutter. With how worked up Castle has gotten her today, she needs to get off, and she needs it bad. She turns on the spray to test the water pressure. It's decent, strong enough for what she wants it for.

Beckett stares at the hook that attaches it to the wall. She shouldn't be doing this. Not in such a public place where anyone from her squad could walk in and hear. After all, she's not exactly quiet when she comes. But she needs the release. And if she doesn't do it now, she'll end up jumping Castle in the middle of the night. As much as she wants to do that, she'd rather wait until they're back home and they have a bed bigger than a twin.

Tentatively, she runs the shower head across her chest, allowing the spray to beat against her skin. Beckett hums, dragging the spray down lower, making a trail of water droplets down her stomach. The spray hits the top of her pubic bone and she drags it around her right hip and lets it trail down her inner thigh. She's never used a shower head for this purpose before, mainly because she's never come across a detachable one, but she's always been curious as to whether or not the sensation is as powerful as some women say it is.

Slowly, she angles the spray up toward her heat. It almost tickles at first, the over sensitive area adjusting to the feeling. She brings the shower head closer, centering it over her clit, and that's when she starts to feel its true affects. Her breath stutters and her eyes slip closed, her left hand reaching out to the shower wall for support. Beckett rolls her hips into the spray, somewhere in the back of her mind pretending that Castle's mouth is what's getting her worked up. Her stomach muscles contract as the first wave of her orgasm hits her. She can't help but cry out as the sensation gets too intense. She's given up on caring if anyone hears her; she's just glad she finally got the throbbing to go away.

* * *

Castle stands outside of the communal bathroom with his toothbrush debating if he should go in there or not. He knows that Beckett is in there taking a shower and after the way they've gone at it today, he's not sure if he could stop himself from joining her. He shakes his head, telling himself that he has more self control than that, and pushes through the bathroom door.

He hears the sounds of a single running shower and instantly knows it has to be her. He can feel his jeans getting tighter at just the thought. Fuck he wants her. Even more so now that he knows there's actually a chance that it's going to happen. That she wants him and his tongue and _fuck_.

Castle turns on the sink and uses it to splash cold water on his face before he runs his toothpaste covered toothbrush under it. He turns the water off and starts brushing trying to think of things that will make him lose his raging hard on. _Dead puppies, his mother, broccoli _–

He freezes, his mouth full of toothpaste, when he hears it. It starts off as a soft whimpering, but it quickly escalates into a moan full of ecstasy. It's Beckett. _Shit_. The woman is in there touching herself, _getting off_, because of him.

_Dead puppies, dead puppies, dead puppies. _

Castle practically growls when he hears her moan again. He swears that time it almost sounded like his name. He starts to wonder if she's done this before, pretended that he's the one touching her instead. That if those sex scenes in Nikki Heat do as much to her as they do to him.

He should honestly just run in there and join her. Take her up against the wall and make her moan his name for real. They'd both feel better, right? But he knows as soon as they open that can of worms, he's going to be addicted to it. Addicted to her. Addicted to making her come and scream his name and to her sharp nails digging into his back.

Fuck.

Castle hears the water turn off. He hears the shower curtain rattling as she reaches around for her towel. He needs to get out of there before she realizes he heard the whole thing. Or maybe he should just run into a shower himself and turn the water all the way to cold. Because clearly thinking of dead puppies is not going to help him tonight.


	3. Chapter 3

They had to do high ropes today. He had to climb up to some height that would no doubt terrify him and his only pillar of support was solely responsible for his inability to focus this morning. He was going to die. He was pretty sure of it. All thanks to Kate Beckett and the sound of her moaning playing on repeat in his head.

"Hey," Beckett says, sliding up next to him, bouncing on her toes.

He drinks her in. Her long, toned legs staring back up at him from beneath those damn shorts that look way shorter than they did to him yesterday. Castle wants those legs wrapped around him. He wants her heels to dig into his back as he –

"You okay, Castle?"

His eyes shift upward toward hers. "No. No, I'm not okay."

He kept quiet last night, pretending to be engrossed in some book by the time she made it back to their cabin. Quite frankly he has no idea what he was reading because the only thing he could focus on was her. And if he's going to go climbing toward his death this afternoon, they need to talk about this.

"I heard you last night," Castle tells her, dropping his voice. "In the shower."

Her face reddens and she shifts her gaze so she's looking at anyone but him.

"You're driving me insane, Beckett. I…I need to touch you."

Her breathing becomes shallow. "So then touch me."

She keeps her eyes trained on Jared as he explains their first warm up activity, but she moves closer to Castle in invitation. His hand slips around her back, dancing around the waistband of her shorts. He feels her lean into his touch. He needs more; he can't do this here.

"Pretend you got stung by a bee," Castle whispers.

"What?" she whispers back.

"Just do it."

Beckett yelps, jumping away from him.

"Son of a bitch," she curses.

"Is there a problem?" Jared asks, starting to head in their direction.

"Bee sting," Castle tells him. "I'll take her to first aid and help her out. You guys go ahead and start. We'll be right back."

Jared nods, turning back to the rest of the squad as Castle grabs Beckett's wrist and pulls her in the direction of the first aid cabin.

"I just bought us a few minutes," he says, pushing open the door and making sure the coast is clear.

"A few minutes for what?" she asks, trailing in behind him.

"For me to touch you."

She bites her lower lip, her eyes growing dark and hooded, and that does it for him. His mouth is on hers in seconds, backing her up against the table. They're both fighting for dominance in the kiss, both of them trying to get the upper hand. Castle tangles one of his hands at the base of her ponytail and gets her to make that same little moan she made the first time he kissed her. This spurs him on further, and he lifts her so she's sitting on the table. She finally lets him take over, opening her mouth to him so he can explore and re-memorize what she tastes like.

As he keeps kissing her, her knees fall open, inviting him into the vee of her legs. Castle presses closer to her and her legs wrap around his hips just like he had envisioned this morning. He drags one of his hands up the bare expanse of her thigh, drawing another moan from her lips.

Beckett shifts her hips against his and nearly gasps when she feels his erection press against her. Castle breaks the kiss to trail his mouth down the bare, inviting, skin of her neck. He guides her head to the side by gently tugging on her ponytail and she obliges. She clings to him as he sucks at her neck and rotates his hips into her, making the most amazing mewling sounds.

She curses, her hips lifting off the table to connect with his as Castle brings his mouth back to hers. He couldn't believe he was dry humping Kate Beckett on the table of a first aid station like some horny teenager. She deserved better than this. But if those noises she's making are any indication, she had no complaints.

He drags his tongue down the other side of her neck, nipping at her earlobe.

"Castle, I –"

She doesn't finish as her mouth gets stuck in a silent scream as her orgasm hits her. He just made her come with of all their clothes still on. Holy hell.

Castle presses his forehead into hers, waiting for her to finish riding it out. Her hips twitch again before she breathes out a sigh of relief. Her hands come up to cup his face.

"What was that?" she breathes.

"I think it was an orgasm. I'll explain how that works later."

She bats his chest, rolling her eyes. "Not what I meant."

"Sounded like what you meant."

"You're still hard," she says, her eyes dropping down to the bulge in his pants.

He shrugs. "Have been all weekend."

"Let me help."

She reaches for the zipper on his shorts, stroking him through the fabric with her other hand.

"Beckett –"

"You were almost there," she says, pulling him out of his boxers. "I could tell by the way you were grunting."

"How do you know what my sex noises sound like?" Castle groans, as she runs her thumb over his tip.

"I know what _men_ sound like. I've brought enough of them close to the edge to know."

"Can you not talk about other men while you're doing that?"

She chuckles, kneeling and dipping her head to draw him into her mouth. Fuck. _Fuck._ Her mouth is on him. Kate Beckett has his dick in her mouth. Castle fists his hand into her ponytail again and looks down at her. She's staring back up at him, doing this amazing thing with her tongue.

His eyes slam shut and his hips shoot forward. She was right, he was close. He comes in her mouth, instantly wishing he could have warned her it was about to happen. But Beckett straightens up grinning, wiping him from the corners of her lips. _She swallowed_.

How the fuck did he end up here with her of all people? How the hell is he this lucky?

"We should get back," Beckett says, looking over her shoulder. "I think you managed to get the stinger out by now."

"Kate."

She spins back to look at him, watching him tuck himself back in his pants.

"Has anyone ever told you how incredible you are?"

She smiles, lacing her fingers through his and squeezing. "Not lately. But it's always nice to hear it."

* * *

"So how's that bee sting doing?" Esposito asks as they head toward the high ropes course.

"It's better," Beckett responds, trying to hide her smile.

"And where'd it get you, your back?" Ryan asks.

She and Castle both nod.

"Interesting, so then what's that on your neck?" Ryan asks.

"Looks like a hickey," Esposito grins.

Beckett's eyes widen and her hand flies up to her neck.

"Some treatment plan you got going there, Castle," Esposito says as he starts to walk ahead. "Remind me not to ask for your help if I ever get stung."

Ryan laughs and starts to walk ahead too.

"We are so busted," Beckett groans, her hand still rubbing at her neck.

"We could always just pretend that it was aliens again."

She groans again, rolling her eyes. "Nice try, Castle. But aliens don't exist anymore now, than they did during that case."

He mumbles something incoherent as they keep walking along. Her arm brushes up against his as the high ropes course comes into view.

"Are you ready for this?" she asks.

"I trust you," Castle tells her as they keep walking. "So yeah. I'm ready."

* * *

He feels like he's making an ass of himself as he tries to climb the ladder to the first platform. This first part isn't even that high, but he's got himself all worked up about it, already afraid to chance a glance at the ground. _For a guy who likes to hang out on the rooftops of buildings, you're being a big wuss. _Castle keeps repeating that to himself because for some reason it seems to help.

"Would it help if you let me climb up there first?" Beckett calls from somewhere below him.

"No," he calls back. "Because then I'd be staring at your ass and I don't need that distraction right now."

He hears her laugh, lets his mind focus on that instead of the climbing, and finally makes it to the top.

"Hey, even Superman had his Kryptonite," Castle says when she makes it to the top, still laughing at him.

"I'm not laughing at you," she says, placing a hand on his arm. "Fear of heights is a pretty natural occurrence within the population."

"What are you the fact police?" he grumbles.

"No, just the regular police."

Castle throws her a look and she smirks, reaching out to attach the zip line clasp to her harness. His hands snake around her waist and hold her back to his chest.

"You realize you can't hold on to me and zip across, right?" Beckett asks. "You have to go on your own."

"I know."

"So then?"

"Didn't want you to fall."

"Thank you, but I'm good to go now."

Castle shakes his head. "No, I think we should just stay here. It's safe here."

"Castle, the faster we get through this course, the faster we can go back to our cabin and…play."

He raises an eyebrow at her. "On twin beds?"

"So we do some redecorating." She spins in his arms the best she can while still being hooked to the zip line. "Or we use them as twins and just get really intimate."

He lets go of her and steps out of her way. "Go. Be free. We have things to do; we don't have time for this."

She grins at him as she double checks her helmet and steps up to the edge. "Think about that as we go through this. It'll help with the height thing."

"What height thing?"

Beckett rolls her eyes and pushes off into the canopy of trees, ready for the day to be done so she can have him alone and all to herself.

* * *

"Took you long enough," Beckett mutters when Castle finally walks into their cabin that night without looking up from her book.

"We were doing man things, Beckett," he tells her, kicking off his shoes by the door. "I couldn't very well let them do it alone."

"But you'd let me do myself alone?"

He stares at her in confusion and she smirks and wiggles her fingers at him.

His face falls. "You started without me?"

"No," she laughs, slipping her bookmark into her book and sliding it under the bed. "But I was about ready to."

"What, the orgasm I gave you this afternoon and the one you gave yourself last night not good enough for you?"

He pulls his T-shirt off over his head and sits on the edge of her bed.

"Only if that PG-13 session we had earlier wasn't good enough for you," she says, her fingers hooking into the waistband of his shorts.

"PG-13? Wouldn't that blowjob make it at least R?"

"Does it matter? I'm just ready for the NC-17 version."

Castle grins and tugs at her tank top. "I like the sound of that."

He draws her mouth in for a kiss, his hands sliding up underneath the back of her top.

"You already took your bra off," he huffs, when his hands touch nothing but bare skin. "I was so looking forward to doing that."

"Guess that means we'll just have to do this again," she smirks, lifting her arms above her head so he can free her of the tank.

"I like the way you think."

He grabs the bottom of the tank and lifts it up, pulling it over her head and tossing it to the floor. His hands cup her breasts, his thumbs rubbing over her peaked nipples. Beckett arches her back, pushing herself further into his palms.

"Someone's eager," he teases, leaning forward to kiss the hickey on her neck he left earlier.

Castle's hands travel south, skimming along her stomach, until he reaches the waistband of her sleep shorts. He hooks his fingers over the edges and pulls, discarding them to the floor as well. He still can't get over the fact that this is happening. That Beckett is lying before him naked and waiting, her hair fanned out on the pillow like some kind of goddess.

"Tell me what you want, Kate."

He loves the way her breath catches when he uses her first name. It's like saying it, calling her that, is an intimate act within itself.

"I want your mouth on me. And I don't want to fake it."

He grins, sliding down so his mouth is hovering over her heat. He kisses his way up her inner right thigh, and then repeats the action on the left. She mewls as he does this, her hips twitching, seeking his mouth. He can tell just by looking at her that she's already wet, her need for him turning him on even more.

Castle swipes his fingers over her swollen nub, before he repeats the action with his tongue. He drags the flat of his tongue upward slowly over and over, until she starts making the most amazing noises. Then he starts licking at her faster, alternating with sucking at her clit. She moans, her hands reaching out to tangle in his hair, as he snakes one hand up to grope at her breast.

He curls two fingers of his other hand inside of her, stroking at her G spot as he continues to work her over with his mouth. Beckett starts to squirm under his touch, his name followed by curse words spilling from her mouth. Her thighs are starting to shake and he knows she's close, so he starts pumping his fingers inside of her faster and focusing his mouth solely on sucking at her clit.

She comes fast and hard, her body shaking from the release. Castle props himself up with his elbows on her stomach, his tongue snaking out to capture her juices from the corner of his mouth.

"Something tells me you weren't faking that," he smirks.

"Fuck," she mutters, her hands already yanking on his shorts.

He laughs and stands up to free himself from the rest of his clothing before he lies back on top of her.

"Aren't you going to ask me what I want?" he husks into her ear.

"And what is it that you want, Castle?" Beckett asks, her nails already scraping over his back.

"I want to be inside of you. And I don't want to fake it either."

She grins. "Shouldn't be a problem."

She grips his waist with her knees and flips them so she's on top.

"I like a woman who knows what she wants," Castle growls, his hands gripping onto her hips.

"Well then, you're going to love me."

Beckett takes him in her hand and slowly settles herself down on top of him. She takes him in fully, sighing at the way he fills her. She twists her hips around him, lifting up until only his tip is inside of her, before she sinks down on him again. Castle moans, his hands now cupping her ass.

But there's only so much of this slow torture he can take and he sits up a little, so she's more in his lap instead of full out straddling him. He pins her arms behind her back and starts thrusting up into her. She lets out a startled gasp at the change in dominance, but soon her back his arching and her head is rolling back in pleasure. Castle takes her arching toward him as an invitation, and draws one of her breasts into his mouth. She moans, rocking her hips against him harder.

He lets go of her pinned arms and flips her so she's on her back again and he can get better leverage. He brackets her head with his arms, as he picks up his rhythm and moves harder and faster. Her hands roam over his back, memorizing each plane of it. Castle draws up one of her legs and lifts it over his shoulder, giving him an impossibly deeper angle to drive into her at. His hand traces her skin down her stomach until it lands on her clit where he starts rubbing tight circles.

She screams his name, breaking apart for him again. Watching her come for him like that is the extra boost he needs to come undone himself. He keeps thrusting into her sloppily until he finishes, her name a whisper on his lips.

Castle starts to roll off to her side, but then he remembers the bed is only a twin and he'd roll to the floor if he did that. So instead, he flips them again so she can lie on top of him instead of the other way around. Beckett settles in against him, burying her head in the crook of his neck.

"You gonna tell me what it is we're doing yet?" Castle asks, threading his hand through her hair.

"I could be wrong, but I think we might be dating."

"Does this mean our days as a crime fighting duo are over?"

"Maybe not," she says, starting to trace shapes into his chest. "Montgomery seems to have a soft spot for you."

He laughs, his other hand skimming up her back.

"How long do you think it would have taken us to get to this point without this weekend?" he asks.

Beckett hums. "I don't know. Without all these trust exercises that call for all of the physical contact…"

He laughs again. "I think we made them more physical than they needed to be."

She shrugs, snuggling closer. "I'm just glad that we made it here. Wherever here is."

"You called it dating, remember?"

"Ah right yes, dating. You going to buy me dinner when we get back to the city?"

"Of course. Especially if we get to do this afterwards."

She places a kiss to his jaw, her lips turning upwards into a smile. "Oh yes, this will definitely be happening again. Because you, unlike some people, most definitely know what you're doing."

Castle smiles, his fingers continuing to dance across her back. "Oh my dear, Beckett. This was only the beginning."

* * *

AN: A huge thank you to everyone who has supported this story! Keep an eye out for a sequel entitled "Sin" that I hope to get out to you either later this month or by September. In the meantime you can follow me on tumblr, URL: tvfanatic, where I'm always answering prompts.


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